1.0 Field of the Invention
The invention relates generally to a metering unit for chemical cleaning agents and cleaning aids, for insuring that such agents and aids are dispensed in a manner to maintain predetermined concentrations for use handling of substances.
2.0 Discussion of Related Art
In the field of hygiene, various substances are used for cleaning and conditioning the cleaning agents and aids. The substances used are often chemical products which are almost always prepared and stored in higher concentrations than are necessary or appropriate for use. Accordingly, they have to be suitably diluted before or during use. In order to be able to maintain the required concentration of the substances in the solution during dilution, the substances have to be delivered in the right amount.
In the institutional sector in particular, difficulties are involved in manually adding the substances in that, this is a labor-intensive task and, the substances used are often substances which can on contact with human skin cause irritation or injury. Because of this, efforts are generally made to mechanize and automate the handling of such substances.
If the substances are present in solid or powder form, a dissolving liquid, for example water, is normally introduced into the storage container so that a certain amount of substance is dissolved and can be put to use. The disadvantage of this procedure is that the concentration of the substances in the solution is very difficult to control. Another disadvantage of dispensers of this type is that the quantity of substance dispensed varies with varying water pressure and, where the water pressure is high, is very difficult to determine.
If the substances are present in liquid form, their concentration is generally well-defined. Accordingly, liquids can be metered by volume to ensure an exact concentration of the liquid in the solution. Metering systems of this type are often very complex arrangements which are difficult to handle. The various units required for carrying out the corresponding process steps have to be clearly arranged in appropriate association and operated accordingly. This calls for considerable alertness and experience on the part of the operator. Accordingly, various attempts have been made to integrate such systems in a neat and compact form and, at the same time, to guarantee a high degree of automation.
WO 95/23549 describes systems in which inter alia the liquid substances are stored and can be automatically delivered to a following pump. The disadvantage of this system is that a refill bag holding the liquid substance remains in the unit until it is empty and the pump is externally arranged. In addition, a very complicated volume control system is required for the pump because excess substance is very difficult to return where metering is based on volume.
3.0 Summary of the Invention
An object of the present invention is to provide a metering unit that includes refill packs that can be removed immediately from a container of the metering unit after filling it with liquid. Another object is to provide the metering unit with means for monitoring the level of the liquid concentrate supply in a holding container thereof. Yet another object of the invention is to provide compact packaging for the metering unit.
In one embodiment of the present invention, with the problems of the prior art in mind, the metering unit includes a chamber with a level sensor arranged below a storage container, the container and the chamber being made liquid-tight to hold the liquid without requiring the presence of a refill bag, and a metering pump being integrated in the metering unit. A metering line leads to a user outside the metering unit, and a return line leads back to the integrated container, whereby one end of each line is connected to the pump.
The present metering unit has the advantage that, because the refill bag does not remain in the unit after it is refilled, the unit can be more effectively emptied. In addition, possible sources of contamination are eliminated by the removal of the bag after filling because the automatic opening of the bag can lead to uncontrolled damage and leakages of liquid. Another major advantage is that a metering pump is integrated into the unit. On the one hand, this enables the returned quantities of liquid to be directly brought back into the storage container by a short route and hence to be re-used. On the other hand, this compact arrangement and, above all, the provision of the level sensor provide for clear and well-organized control and automation.
Since it is impossible to prevent impurities from entering the system, for example through incompetent destruction of the refill bag or through soiling thereof, an embodiment in which a fine-mesh sieve is provided between the container and the pump is particularly advantageous. The positioning of this fine-mesh sieve in the outlet opening of the container is preferred.
The level sensor is designed in such a way that it can differentiate between different filling levels, this can be used very effectively to indicate readiness for use when the filling level is normal, and to generate a refill signal when a predetermined lower filling level is reached. In one particularly advantageous embodiment, the metering unit is automatically switched off when a minimum filling level is reached to avoid errors and possible damage to or destruction of the metering pump this way. In a preferred embodiment, the level sensor is a float switch.
In another particularly advantageous embodiment provided by integration of the metering unit, a piston diaphragm pump is used as the metering pump. This provides for the stepless control of metering integrated in a simple and favorable manner.